4 ms·

https://www.instructables.com/id/Yellow-Dots-of-Mystery-Is-Your-Printer-Spying-on-/ https://www.instructables.com/id/Yellow-Dots-of-Mystery-Is-Y... "Most color

https://www.instructables.com/id/Yellow-Dots-of-Mystery-Is-Your-Printer-Spying-on-/ https://www.instructables.com/id/Yellow-Dots-of-Mystery-Is-Y... "Most color laser printers and color copiers are designed to print invisible tracking codes across every single printed page of their output. These codes reveal which machine produced a document and, in some cases, when the document was printed or copied." FYI Edit: List of Printers Which Do or Do Not Display Tracking Dots https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots https://www.eff.org/pages/list-printers-which-do-or-do-not-d... I'm going to have a close look at my monochrome laser printer output, just in case.

vuln 6y ago
This is exactly how they were able to figure out the NSA’s Reality Winner leaked sensitive data. https://arstechnica.com/information-technology/2017/06/how-a-few-yellow-dots-burned-the-intercepts-nsa-leaker/ https://arstechnica.com/information-technology/2017/06/how-a...
tenebrisalietum 6y ago
Always wondered if this was defeated by ensuring the entire page uses maximum yellow color edge-to-edge with 0 margin. The background wouold have to be full saturation yellow, and your text would have to be full saturation green or orange to ensure yellow is printed where text or monochrome images is printed (unless it's impossible to detect yellow dots mixed with black ink).
- ncmncm 6y ago
  Not good enough. It might print a pattern of white pixels too. You need a yellow random-halftoned background. I would not be surprised to learn that this also is defeated by some kind of FFT scheme used just for such images. There is plenty of room for code of practically unlimited sophistication. Got to figure anything you print is compromised, which might be an intended point.
sbierwagen 6y ago
Monochrome laser output will also be fingerprinted by the uneven toner pattern from wear on the drum and the toner transfer roller.
- throwaway_pdp09 6y ago
  I've heard this (well, about the drum, but the transfer roller?) but it's incidental and can be changed by changing the drum, and is not an intentional tracking device that encodes date of printing, device ID etc. such that some DB can be used to track it.
  - sbierwagen 6y ago
    Transfer roller, of course. Note how print quality degrades as you get towards the bottom of a toner cartridge on a cheap printer, the consistent pattern of print artifacts. >changed by changing the drum Sure, it depends on the threat model. If you're producing many documents some time apart, replacing drums and cartridges could be a purchase signal in of itself. If you're doing something very risky, like publishing nuclear weapon plans, ISIS recruitment flyers, or Clinton foundation invoices, then leaking just a few bits of identifying information could be life-ending. Cf https://www.gwern.net/Death-Note-Anonymity https://www.gwern.net/Death-Note-Anonymity
- deleted 6y ago
  [deleted]

vuln 6y ago

This is exactly how they were able to figure out the NSA’s Reality Winner leaked sensitive data. https://arstechnica.com/information-technology/2017/06/how-a-few-yellow-dots-burned-the-intercepts-nsa-leaker/ https://arstechnica.com/information-technology/2017/06/how-a...

tenebrisalietum 6y ago

Always wondered if this was defeated by ensuring the entire page uses maximum yellow color edge-to-edge with 0 margin. The background wouold have to be full saturation yellow, and your text would have to be full saturation green or orange to ensure yellow is printed where text or monochrome images is printed (unless it's impossible to detect yellow dots mixed with black ink).

ncmncm 6y ago
Not good enough. It might print a pattern of white pixels too. You need a yellow random-halftoned background. I would not be surprised to learn that this also is defeated by some kind of FFT scheme used just for such images. There is plenty of room for code of practically unlimited sophistication. Got to figure anything you print is compromised, which might be an intended point.

sbierwagen 6y ago

Monochrome laser output will also be fingerprinted by the uneven toner pattern from wear on the drum and the toner transfer roller.

throwaway_pdp09 6y ago
I've heard this (well, about the drum, but the transfer roller?) but it's incidental and can be changed by changing the drum, and is not an intentional tracking device that encodes date of printing, device ID etc. such that some DB can be used to track it.
- sbierwagen 6y ago
  Transfer roller, of course. Note how print quality degrades as you get towards the bottom of a toner cartridge on a cheap printer, the consistent pattern of print artifacts. >changed by changing the drum Sure, it depends on the threat model. If you're producing many documents some time apart, replacing drums and cartridges could be a purchase signal in of itself. If you're doing something very risky, like publishing nuclear weapon plans, ISIS recruitment flyers, or Clinton foundation invoices, then leaking just a few bits of identifying information could be life-ending. Cf https://www.gwern.net/Death-Note-Anonymity https://www.gwern.net/Death-Note-Anonymity
deleted 6y ago
[deleted]